Species richness, habitat association and odonata diversity of the south-western region of Bangladesh.

Odonata survey was conducted throughout the south-western region of Bangladesh, concentrated on eight districts and the Sundarban (the largest mangrove forest of the world) from August 2014 to August 2016. A total of 50 species under 30 genera belonging to six families were recorded during the study period. Among the 50 species, 31 species belong to Anisoptera whereas 19 species were recorded from the Zygoptera suborder. Libellulidae and Coenagrionidae were most dominant Anisoptetran and Zygopteran families with 28 and 17 species respectively. One Zygoptera species Mortonagrion varalli was newly added to the Odonata fauna of Bangladesh. Among surveyed habitats, species richness was highest in marshland with 38 species followed by 34 species in the lakeside. On the other hand, odonata diversity was lowest in the mangrove area. Our study shows a positive correlation between environmental variables (such as average rainfall, relative humidity, and average temperature) and species richness in the study area. Species richness is highest during monsoon and lowest in winter.